350 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1937 



4. CENTRAL AMERICA 



The Central American fish fauna is a strange mixture of Nortli and 

 South American typcs.'^ Of the purclj^ North American fishes, the 

 garpikes have gone farthest south, having reached Lake Nicaragua, 

 and their invasion was Ukely a fairly old one. The ameiurid catfishes 

 and the suckers have gotten as far as Guatemala, the carps to centra! 

 Mexico, and the perches and sunfishes only to northern Mexico. Of 

 the South American families, the loricariid, astrohlepid, callichthyid, 

 and pygidiid catfishes, and four of the five families of Neotropical 

 characins have gotten only a slight hold in Panama and Costa Kica. 

 The gymnotid eels range north to Guatemala, the pimelodid catfishes 

 to southern Mexico and Yucatan, the cichlids to Texas and the fifth 

 family of characins to New Mexico. None of these northern or 

 southern invaders save the cichlids has produced many startling 

 endemic fonns in Central America. The genera are few in numher, 

 almost all identical with those in North or South America, and rep- 

 resent merely a few of the most aggressive frontiersmen of dominant 

 famiUes. 



In the cichlids, however, there has been an extremely rich flower- 

 ing of species of the South American genus Cichlasoma, some of them 

 distinct enough to be placed in difl"ercnt genera. But the cichlids arc 

 probably among the youngest of the coterie of fresh-water fish families, 

 and their active recent evolution in the African lakes makes it seem 

 probable that their numerous, closely related. Central American rep- 

 resentatives are rather young. Certain it is that the South American 

 Cichlasomas are less specialized than the Central American. 



It is among the top-minnows or cyprinodonts that we find the most 

 distinctive Central American fresh-water fishes. The most primitive 

 living genus of the oviparous family Cyprinodontidae (Prqfundulus) 

 is confined to southern Mexico and Guatemala, and from ancestors 

 not vcr}' dilFcrent from it probably arose the peculiar viviparous family 

 Goodcidae, which is practically confined to the Rio Lerma Basin in 

 Mexico. Returning momentarily to the Cyprinodontidae, a peculiar 

 genus (Garmanclla) related closely only to a Florida form {Jordanella) 

 occurs in Yucatan, and the remarkable Oxyzygoncctes is found only in 

 Pacific Costa Rica; both are related to northern types, as is Projundu- 

 lus. Of the southern rivuline group, Rivulus alone is found, as far 

 north as Yucatan. Of the more advanced viviparous cyprinodonts 

 (Poeciliidae), Central America has a great profusion of endemic species 

 and genera, many of them very peculiar. At least one subfamily 

 (Poeciliopsinae) is practically confined to the region, overfloAnng 

 sliehtly into Arizona and Colombia. The most highly specialized 

 genera, as well as some of the most generalized, occur in Central 



" See especially Re^an (1908) for a discussion. 



